johnson



3 Sheets-Sheet 1 E. H. JOHNSON ROTARY FLUID PRESSURE ENGINE Inventor ED -unfit: Harmv Touwsou B any ,W Mm?) Attorney Feb. 21, 1956 Filed Nov. 21, 1951 Feb. 21. 195

3 Sheets-Sheet 2 Filed Nov. 21, 1951 Feb. 21. 1956 Inventor E'DwHRb Ham-w T uwsou B 271a? F614) Attorney United States Patent 2,735,371 ROTARY FLUID PRESSURE ENGINE Application November 21, 1951, Serial No. 257,446 11 Claims. (Cl.'103-125) This invention relates to rotary'fiuid pressure engines, whether they be pumps or motors, of thekind comprising a casing in which is provided an annular blade chamber, a'rotor having blades which extend across the bla'dechamber so as to make a sealing fit with'the inner and outer circumferential walls of the "blade chamber relatively to which the rotor rotates about the axis of the blade chamber, at least one rotary abutment extending across the blade chamber between inlet and outlet jports with its axis parallel 'to the axis of the rotor lying in and making a sealing fitwith the walls of an abutment chamber consisting mainlyof an abutment recess, hereinafter calledfthe larger abutment recess, in the one of the circumferential walls of the blade chamber, but also partly of an "abut- 'ment recess, hereinafter referred to 'as the smaller abutment recess, in the other circumferential wall of the 'blade chamber, the abutment'being provided'with pairs of diametrically opposite recesses in its periphery all of the same circumferential dimensions, two or more of such recesses constituting blade-receiving recesses each of which during rotation of the abutment comestinto posi- 'tion to receive a blade and permit it topass'theabutment as the blade during its rotation comes to the part ofthe blade chamber across which the abutment extends, and two pressure balancing recesses provided in 'the circumferential surface of the larger abutment recess and lying diametrically opposite the parts of the 'a'butmentwhich are exposed respectively to the pressurein'the :highand low pressure parts'of the'blade chamber, the area of each "pressure balancing recess measured at "the-circumference of the abutment being equal to the diametrically opposite area exposed to the interior of the blade chamber and such that it communicates at all times with one or other of the recesses in the abutment and each recess in the abutment being connected by a passage in the abutment with the diametrically opposite recess.

In certain applications of pumps and motors of the above kind it is important that the fiow'offiuid through the pump or motor shall bear and maintain a close relationship to the angle of rotation of the rotor'even at very low speeds, and that this relationship shall'be maintained throughout each individual revolution of the rotor.

It Will be appreciated that the maintenance o'fsuch an exact relationship, especially at low rotational speeds, cannot be achieved if there are appreciable variations in the rate of leakage through the clearance'spac'es of the pump or motor exposed to the pressure in the-working chamber during each revolution,'and it is the object of the present invention to provide an arrangement, which will tend to reduce to a minimum variations in the relationship between fluid flow through the pump or motor and rotation of the rotor and thus be particularly but 'not exclusively applicable to so-called sensitive pumps and motors, "that is pumps and motors in which 'it is important 'to maintain a-substantially fixed relationship between rate of'fiuid'flow and angle of rotor-rotation.

To -'this end according to the :present 1' invention the di- -mensions of the inlet and :outletzp'o'r'ts':ofaaipumpaorsmotor of the kind referred to where they open into the blade chamber are such and/or the inner Wall of the blade chamber 'and/ or larger abutment recess-adjacent to such ports is so cut away thatfor all rotational positions of the blades and vabutment the total-circumferential lengths of sealing contact 'between the "blades and the inner and outer walls of the blade chamber and betweenthe abutment and each of the abutment recesses remain-unchanged throughout the rotation of the parts.

Thus "the are over which extend the parts of theinner and outer circumferential wallsto'f the blade chamber with which the blades in their travel make sealing contact is equal to the angle between the blades in the case of a two blade rotor or between any two adjacentblades in rotorshaving more'than 'twoblades.

Furthertin some cases'in order to maintain the sealing area between the abutment and the larger and smaller abutment recesses respectively constant throughout the rotation-of the abutment, it may be necessary to provide in each of these recesses cut-away parts constituting nonsealing areas of the same width as each of the areas of the abutment exposed to the pressure in the blade chamber, 'thatis to say the area of'the communicating opening between either side of the'blade chamber and theabutment chamber. 'While moreoverfor pressure balancing or other reasons it may be necessary or desirable to provide certain non-sealing areas on the circumferential surface of the abutment between the'blade-receiving recesses. Thus in preferred arrangements in a pump or motoro'f the'kind referred to according to'the invention the surface of the abutment chamber constituted by the larger and smaller abutment recesses is dividedcircumferentially into a series of equally spacedsealing areas of equal circumferential length separated .by equally spaced non-sealing areas and the circumferential surface of the abutment is divided circumferentially into a series of equally spaced sealing areas of equal circumferential width. separated by equally spaced non sealing areas constituted wholly or as to some of them 'only,by the blade receiving recesses, the relative circumferential dimensions of the sealing and non sealing areas respectively on the abutment and the surface of the abutment recesses being such that at each moment duringrotation when any sealing area on the abutment "breaks engagement with a sealing area in either of the abutment recesses, the abutment sealing area in rear thereofin the sense of rotation comes into the positionin which ithas its maximum area of engagement with the appropriate sealing area 'in the abutment recess.

'It will be seen that the arrangement so far described ensures that the circumferential sealing areas between the high and lowpressureparts of the pump or motor-both in the blade chamber and in the abutment recesses remain constantthroughout rotation ofthe rotor and abutment so that, under any given conditions the rate of leakage through the circumferential seals tends to remain constant and thereby to maintain an exact relationship between fluid flow and angle of rotor rotation throughout eachrevoluti0n of therotor.

tittalso tends to ensure substantially constant leakage through .the clearance spaces between the blades and the ends of the working chamber with which they make a'sealingfit by providing a constant area of seal subject respectively to the high and low-pressuresat these points. There are, "however, other working clearances the areas .of which subject to the higher pressure vary during operation, namely the arcuate sealing area between 'the abutment and the smaller abutment recess at the point where the abutment enters the working chamber, since this :arcuate sealing area will, when a recess in the abutment .-.i n itraversing tit and is in :communication with :the-rhigh pres'sure Iside 10f the working chamber, have a relatively large area subject to high pressure while when a recess in the abutment is traversing it and comes into communication with the low pressure side of the working chamber the arc will be mainly subject to low pressure. Similarly with some constructions the length of the circumferential sealing surface between the end of the abutment and the wall of the casing through which it or a shaft driving it enters the abutment chamber which is subject to the higher pressure may vary with rotation of the abutment due to the arrangement and spacing of the recesses in the abutment which at different times are in communication respectively with the high pressure and low pressure sides of the working chamber. This latter difiiculty can be reduced by providing a number of blade-receiving recesses in the abutment, for example four, such that at all times the mean pressure in the recesses in the abutment is constant whereby on sum there is no leakage to or from the abutment chamber although there may be a constant leakage between the various recesses across the end face of the abutment chamber.

Moreover, a circumferential seal may be provided around the shaft by which the abutment is driven and which passes through the end face of the abutment chamber.

In order to ensure still further that little change in mean leakage shall occur due to the variations in the length of the sealing paths exposed to pressure during rotation of the rotor and abutment, the pump or motor will preferably be provided with a closed casing filled with the working fluid, into which casing the various working clearances open so that any leakage through a clearance area for the moment subject to high pressure tends to build up pressure in the casing, while leakage through a clearance area subject to low pressure tends to permit leakage from the casing. Thus the pressure in the casing tends to vary according to the relative lengths of leakage paths from the high pressure side to the casing and from the casing to the low pressure side, and this being so the total rate of leakage tends to remain constant.

Various forms of hydraulic pump or motor incorporating the invention are illustrated by Way of example in the accompanying drawings, in which Figure l is a sectional side elevation of one form of pump or motor according to the invention having a four blade rotor,

Figure 2 is a cross section on the line 2-4 of Figure 1,

Figure 3 is a similar view to Figure 2 showing how the invention may be applied to a pump or motor having a two blade rotor, and

Figure 4 is a similar view to Figure 2 showing how the invention may be applied to a pump or motor having a three blade rotor.

In the construction shown in Figures 1 and 2 the pump or motor comprises a block A constituting the body of the pump or motor proper sandwiched between two end cap or casing members B and C which in conjunction with the circumferential part of the block A form a fluid tight casing enclosing the working parts of the pump or motor proper.

The block or body part A has formed therein two parallel intersecting cylindrical bores D and E adjacent end portions D1 and E1 of which constitute respectively the outer circumference of the working chamber D and the larger abutment recess.

Secured by bolts F to one end of the block A within the casing part B is an end member F having a partcylindrical projection F which projects into and makes a fluid tight seal with part of the circumference of the bore D and has a part of reduced diameter F at its end which constitutes the inner circumferential wall of the working chamber D Inlet and outlet passages passing through the block A communicate with the working chamber D The projection F is less than a complete cylinder in that it has an arcuate recess E in its circumferential surface constituting the smaller abutment recess and therefore having a part cylindrical surface which constitutes in effect a continuation of the part cylindrical surface of the larger abutment recess E Also secured to the end face of the block A enclosed by the casing part B is an end member G having a cylindrical part G at one end which projects into the bore E, regarding this as including the recess E and forms one end face of the abutment chamber.

The opposite end face of the abutment chamber is formed by an end plate H secured to the face of the block A within the casing part C and having a hollow boss portion H the bore of which is coaxial with the bore D of the working chamber D and includes a part 1-1 which opens into the working chamber D and has the same diameter as the outer circumference D of the working chamber, and an outer part which is of somewhat larger diameter than the outer circumference of the working chamber.

Disposed coaxially with the working chamber D and supported in bearings J at one end in the end member F is a rotor shaft K carrying a rotor, K having a cylindrical part K making a close seal with the part 1-1 of the bore of the boss H from which cylindrical part project four blades K of the cross sectional form shown in Figure 2.

The bore of the cylindrical part K of the rotor makes a fluid tight seal with a ring F secured to the end of the part F The rotor K which is keyed to the shaft K, is supported in roller bearings I so that the whole rotor shaft and rotor assembly K, K is carried by the bearings I and J The shaft K projects through a fluid tight gland K in the casing part C. Mounted in the abutment chamber is a rotary abutment L of the cross sectional form shown in Figure 2 so as to have four blade-receiving recesses L, the abutment being mounted on an abutment shaft L one end of which is supported in bearings L in the end member G while its other end has rigidly mounted thereon a gear wheel M supported in a bearing L in the member G. The gear wheel M meshes with a gear wheel N of the same pitch diameter on the rotor shaft K so that the rotor shaft K and abutment shaft L during operation rotate in opposite directions at the same rotational speed. The arrangement is such that in known manner one of the blade-receiving recesses L comes into position to receive a blade K and permit it to pass the abutment L each time a blade reaches the point in the working chamber D across which the abutment L extends.

V Formed in the abutment L are passages, O, 0 connecting opposite blade-receiving recesses L to one another and also passages indicated at O and O in Figure 2 extending between diametrically opposite points in the circumferential surface of the abutment L disposed midway between the edges of adjacent blade-receiving rccesses L Formed in the abutment receiving recesses E and E are grooves E each having a circumferential width equal to that of each of the areas E E over which the abut ment is directly subject to the pressure in one side or the other of the working chamber D The arrangement is such that each groove E is permanently maintained in communication with its diametrically opposite groove E or space E or E by the passages O, 0 O and O Moreover the dimensions are such that the circumferential width of each blade-receiving recess L is equal to the sum of the circumferential width of each non-sealing groove E or space E or E and the circumferential width of each of the sealing surfaces L between adjacent edges of the grooves E and spaces E E It will therefore be seen that as that abutment L rotates the length of circumferential seal between it and the surface of the smaller abutment receiving recess E will remain constant and that similarly the total length of circumferential seal between it and the surface of the rmsa sr'i -35 larger abutment receiving "recess E will remain constant and in such mannerthatfthe total circumferential length of sealing.areabetween any two adjacent spaces subject respectively to inlet andoutlet pressure 'remains constant. Each'of the inlet and outlet passages D and D opens into 1thewo'rking .chamber through a port having .a circumferential width such that theedges of those .portsremotefrom the abutment L lie in. a plane containing the axis of'the working chamber and at right angles to the commonplane in which theaxes "of the rotor and abutment lie. It Will'beseen that With'this arrangement the total area of seal between the outer circumferential surfaces of the blades atanyrnoment voccupyingithe workingchamber D and the outericircumferential wall of this chamber.will be constantthroughout'the rotation of the rotor.

Similarly the inner circumferential wall of the working chamber is cutaway asrindica'ted at P so.that its sealing surfaceterminatesinthesame place as the edges :of 'the parts referred "to above "and the total area of the seal between the "inner circumference of the working chamber'therefore also remains constant throughout the rotationof the rotor.

In order 'stillfurth'er to tend to maintain a constant degree of leakage through any clearance spaces during rotation of .the parts 'offthepump or motor not only is the'casing made liquid 'tightandifilled with working liquid so thatfflow 'to 'andfrom it 'through'any clearance spaces opening into it tends to beresisted by reason of the build up or reduction in pressure thus caused, but a 'fiuid seal of some known'type is provided around the abutment shaft as indicated at "P In the modified construction shown in Figure 3 the pump .or motor mig'htotherwise be of the same general construction as that s'hownin Figures 1 and 2 but the rotor has only (two blades as indicated at Q, and the abutmentfR has therefore only two blade-receiving recesses as indicated at'R and in addition flats R each of the same circumferential width as a recess R In this construction it will be seen that the diametrically opposite recessesYR and chambers formed by the flats R communicate with one another through passages indicated at R while grooves S are formed in the circumferential wall of the larger abutment receivingrrecess S each of the same circumferential width as and lying diametrically opposite to one of "the openings S through which the abutment R is exposed to 'thepressures in the working chamber.

Each of 'the sealing surfaces S which separate the grooves S and openingsQS from one .another has a circumferential width equal tojthe sum of the circumferential width of .eachof the recesses R and -.the circumferential width of eachof the sealing surfaces 5* on the abutment which separate adjacent non-sealing recesses R andfflatsTR fromone another, while the circumferential width of the surface S is equal to that of each of the surfaces S Thus,zas-the abutment R rotates the total circumferential length of sealing area between it and the smaller abutment receiving recess S remains constant and the total circumferential length of sealing area between the abutment and the larger abutment recess 8 remains "constant -in such manner that the circumferential' length of each sealing area on the abutment between any space 'or chamber rim-communication with the high pressure side of the ,pump or motor and any adjacent space or "chamber in communication with the low pressure side of the pump or motor remains constant.

It will moreover be seen that the edges of the inlet and outlet passages remote from the abutment extend to a plane containing the axis of the rotor and that the inner wall of the working chamber is also cut away as indicated at T so that in effect both circumferential walls of the part of the working chamber with which the blades make a sealing fit during their rotation terminate in the plane mentioned and hence the total eifective length of circumferential seal the sealing *6 provided between the blades and theWatlls of 'the'work-ing chamber remains constant throughout the rotation of the rotor.

*In the construction shown in Figure 4the pump or motor'mightotherwisebe similar to that shown in Figures l and 2 *but "has a three bladed rotor and a three recess abutment U and the abutment receiving recesses and the working chamber so formed as to provide the desired constant areas of circumferential seal. 'Thus in this construction the larger abutment receiving recess V is'provided with-two fgrooves V each of the same circumferentia'l "length as and lying diametrically opposite. to one "of the spaces V *at'which the abutment is exposed to the pressure in the working chamber, the

groovesiV being separated by a circumferential sealing surfacev 'equal in circumferential length to each of the circumferential sealing-surfaces V between a groove V and the-adjacent space V and also to the circumferential length of the smaller abutment receiving recess V The abutment in this construction has, more- 'over, formed on its circumferential surface three flats U each of the same circumferential width as and diametrically opposite to one of the blade-receiving recesses U with passages U connecting each recess U to itsopp'osite fiat U The-circumferential width of each and V is equal to the sum of the circumferential width of each of the recesses U andflats U 1 plus the circumferential width of any one of surfaces on the abutment between an edge of a'blade-receiving recess U and the adjacent edge of "In this construction also the inner and outer circumferential walls of the working chamber are formed so that the effective are over which the surfaces which make "sealing engagement with the blades during rotationbf the latter subtend an angle of only whereby "the circumferential length of the total sealing surfaces between the blades and the walls of the working chamberremains constant throughout rotation of the rotor.

Although-theinvention has been described with particular reference to rotary pumps or motors of the kind referre'd-to having-a singleabutment, itwill be understood that it is equally applicable to such pumps and motors havingtwoabutments and therefore two sets of inlet and outlet ports.

fingfit with .theinner and outer circumferential walls thereof relatively "to which'the rotor rotates about the axis of the blade chamber, and at least one rotary abutment with its axis parallel to the axis of the rotor extending across the blade chamber between the inlet and outlet ports and lying mainly within and making a sealing fit with an abutment receiving recess in one of the circumferential walls of the blade chamber and making a sealing fit with a second abutment receiving recess in the other circumferential Wall of the blade chamber, said recesses being of the. same diameter butsubtending different arcs, the abutmentcontaining in'its periphery recesses at least some of which are arranged to come into position to receive a blade and permit it to ;pass the abutment as it comes to 'the'point at which the abutment extends across the blade chamber, said peripheral recesses being arranged in diametrically opposed connected pairs constituting pressure equalizing openings between sealing parts of the abutment wherein the dimensions of the parts are such that the total circumferential widths of sealing engagement between the blades and the inner and outer walls of the blade chamber and between the abutment and each of the abutment receiving recesses remains unchanged throughout rotation of the rotor and abutment, whereby the rotational speed of the rotor for a fixed rate of flow is maintained substantially constant at all angular positions of the rotor and vice versa. 7 a g u 2. A rotary pump or motor of a type comprising a casing enclosing an annular blade chamber having inlet and outlet ports, a rotor having blades which extend across the blade chamber and make a sealing fit with the inner and outer circumferential walls thereof, relatively to which the rotor rotates about the axis of the blade chamber, and a rotary abutment extending across the blade chamber between the inlet and outlet ports and making a sealing fit with a larger part-cylindrical abutment receiving recess in one of the circumferential walls of the blade chamber and a smaller part-cylindrical abutment receiving recess of the same diameter in the other circumferential wall of the blade chamber, the abutment having blade receiving recesses in its periphery disposed diametrically therein each of which comes into position to receive a blade and permit it to pass the abutment as it comes to the point at which the abutment extends across the blade chamber, wherein the are over which extends the parts of the inner and outer circumferential walls of the working chamber with which the blades make a sealing fit during their rotation subtends an angle at the axis of the rotor evenly divisible by that between adjacent blades, while the surface of the abutment chamber constituted by the larger and smaller abutment receiving recesses is divided circumferentially into a series of equally spaced sealing areas of equal circumferential length separated by equally spaced non-sealing areas and the circumferential surface of the abutment is divided circumferentially into a series of equally spaced sealing areas of equal circumferential width separated by equally spaced non-sealing areas, the relative circumferential dimensions of the sealing and nonsealing areas respectively on the abutment and the surface of the abutment receiving recesses being such that at each moment during rotation when any sealing area on the abutment breaks engagement with a sealing area in either of the abutment receiving recesses, the abutment sealing area in rear thereof in the sense of rotation comes into the position in which it has its maximum area of engagement with the appropriate sealing area in the contiguous abutment receiving recess, whereby the rotational speed of the rotor for a fixed rate of flow is maintained substantially constant at all angular positions of the rotor and vice versa.

3. A rotary pump or motor of the kind referred to as claimed in claim 2 in which the rotor has four blades and the abutment has four blade-receiving recesses and the circumferential width of each sealing area on the abutment between the adjacent edges of adjacent blade receiving recesses is equal to the sum respectively of the circumferential width of each of the non-sealing areas of the abutment receiving recesses and the circumferential width of each of the sealing areas in the abutment receiving recesses.

4. A rotary pump or motor as claimed in claim 3 in which passages are provided in the abutment whereby each pair of diametrically opposite non-sealing areas both in the abutment and in the abutment receiving recesses are maintained continuously in communication with one another.

5. A rotary pump or motor of the kind referred to as claimed in claim 2 in which the rotor has two blades and the abutment has two blade-receiving recesses with two non-sealing areas and three sealing areas on each of the two circumferential surfaces of the abutment extending between the recesses, and the larger abutment receiving recess has two non-sealing areas each lying diametrically opposite to and having the same circumferential width as one of the spaces through which the abutment is subject to the pressure in the working chamber, and in which the circumferential length of each ofthe sealing areas in the larger abutment receiving recess is equal to the circumferential width of the smaller abutment receiving recess and to the sum of the circumferential width of each of the blade receiving recesses and the circumferential width of one of the sealing areas on the abutment.

6. A rotary pump or motor as claimed in claim 5 in which passages are provided in the abutment whereby each pair of diametrically opposite non-sealing areas both in the abutment and in the abutment receiving recesses are maintained continuously in communication with one another. i

7. A rotary pump or motor of the kind referred to as claimed in claim 1 in which the rotor has three blades and the abutment has three blade-receiving recesses with a non-sealing area on the part of the circumference of the abutment between each adjacent pair of blade-receiving recesses, the larger abutment receiving recesses has two non-sealing areas lying respectively diametrically opposite to and having the same circumferential width as each of the spaces through which the abutment is subject to the pressure in the working chamber, and in which the circumferential width of each of the sealing areas in the larger abutment receiving recess and of the sealing area of the small abutment receiving recess is equal to the sum of the circumferential width of each of the blade receiving recesses and the circumferential width of each of the sealing areas on the abutment.

8. A rotary pump or motor as claimed in claim 7 in which passages are provided in the abutment whereby each pair of diametrically opposite non-sealing areas both in the abutment and in the abutment receiving recesses are maintained continuously in communication with one another.

9. A rotary pump or motor as claimed in claim 1 including a closed pressure casing enclosing the working parts of the pump, arranged to be maintained full of working liquid and into which the working clearances at the ends of the rotor and abutment open.

10. A pump or motor as claimed in claim 9 wherein the abutment has a hub which extends axially from the abutment chamber and by which the abutment is driven, said hub having a working clearance between it and the surrounding casing, and a circumferentially extending pressure seal arranged in said working clearance.

11. A pump or motor as claimed in claim 2 wherein the abutment has a hub which extends axially from the abutment chamber and by which the abutment is driven, said hub having a working clearance between it and the surrounding casing, and a circumferentially extending pressure seal arranged in said working clearance.

References Cited in the file of this patent UNITED STATES PATENTS 

